From Sahih Bukhari (Hadith 348):
Narrated `Imran bin Husain Al-Khuza`i:Allah's Messenger (ﷺ) saw a person sitting aloof and not praying with the people. He asked him, "O so and so! What prevented you from offering the prayer with the people?" He replied, "O Allah's Messenger (ﷺ)! I am Junub and there is no water." The Prophet (ﷺ) said, "Perform Tayammum with clean earth and that will be sufficient for you
Reference: Bukhari 348